In the case where thick-plating is applied on a wire material in an applied amount of not less than 400 g/m2 through molten zinc plating or molten zinc-aluminum alloy plating, it is difficult to obtain a plated wire material with good outward appearance having a uniform thick plated layer, due to the movement of the applied plated layer through the vibration generated during the course of transferring the wire material itself before coagulation. This leads to a thickness deviation ratio, which is a value obtained by dividing the maximum thickness of the plated layer by the minimum thick layer) arriving at from 3 to 5, causing a problem in terms of insufficient linear/diameter tolerance, deterioration of anti-corrosion properties and the like.
We have developed apparatuses for plating a wire material disclosed in Japanese Patent Laid-Open No. 10-60615 and No. 11-323524, and have conducted improvements where adhered molten plated layer is allowed to cool down by a forcibly cooling device in the same apparatus to decrease the flowability, whereby a plated wire having a uniform thick plated layer and good outward appearance can be obtained.
As a result, the use of such apparatuses makes it possible to improve a thickness deviation ratio of 2.0 or less. However, it has been difficult to produce a plated wire having a thickness deviation ratio of 2.0 or less in a stable manner.
In addition, the forcibly cooling device described above can only pass one wire, resulting in poor productivity. Further, at the time of the breakage, a lot of loss is caused during the course of again passing the wire, and at the time of detaching the cooling device, there is a problem in terms of workability such as cutting off the plated wire.